1. Technical Field
The present invention relates to cellular telecommunications networks and in particular, to cellular telecommunications networks in which local traffic (calls and/or messages) may be provided between users in a cell area or group of cell areas.
2. Description of Related Art
Cellular network operators are deploying their networks across more and more remote areas. Consequently, instability on transmission links, which are part of the radio access network, i.e. the Base Station System (BSS) in case of 2G networks or the RAN in case of 3G networks, is becoming a common problem. In emerging markets, this instability is typically due to the more challenging requirements placed on network links, such as those arising from distance, terrain, improper maintenance, bad quality transport networks, etc. Due to this instability, users suffer from frequent service outages. This undermines customers' confidence in the service and it has an economical impact, both for users and operators. So, it would be desirable to provide a solution which is able to alleviate transmission problems and provides service with an acceptable level of quality in remote areas.
There have been several attempts at minimizing used transmission bandwidth in the cellular communication network for isolated/rural coverage and in order to address the impact of transmission link instability. Two broad approaches can be distinguished.
The first approach, which is referred to as “Local Switching” is a radio network functionally that allows switching user plane traffic information flow through the access node (BTS) when a call is established between parties camped in the same BTS coverage (refer to 3GPP work item CP-090812, Release #10). Control plane information (i.e. signalling) is still conducted towards other access nodes: BSC and Core. Thanks to this functionally some savings in transmission bandwidth links are obtained. An example of how this local switching works is depicted in FIG. 1: a 2G cellular communication network 10 comprises access nodes 20 (BTSs), radio control nodes 30 (BSCs) and a Core Network 40. Voice calls 60 between mobile users 50 in the same cell area covered by one of the access nodes or in the cell areas of a cluster of access nodes, are switched locally. However, the signalling 70 proceeds up to the core network 40.
This results of course in a considerable reduction of the used transmission bandwidth in the radio access network, because the forward and backward voice transmission connection from the access node 20 to the core network 40 can be dispensed with. Furthermore, this solution has no impact on VAS (value added services) provided by the cellular communication network. They can be provided in a conventional manner by the core network, because the signalling messages from and to the mobile station involved in the intra BTS voice call are at its disposal. Finally, there is no need for a fundamental architecture change of the cellular network.
However, a transmission link failure in the access network results in a complete service outage because the signalling can no longer reach the core network. Furthermore, local business models, wherein the billing and call provisioning of the users 50 are managed locally, are not possible.
The second approach, which is referred to as “Network in a Box”, provides a local system which is designed to provide emergency or temporary network to provide coverage after a disaster. This solution includes a functional pre-configured core network that offers routing, authentication and radio access network management. Node B options and expansion kits allow customers to create a custom network that meets their needs.
FIG. 2 schematically illustrates certain features of an implementation of this second approach. In this case, the radio control node functionality 30′ and core network functionality 40′ are collapsed for an access node 20 or cluster of access nodes. Voice calls 60 between local mobile users 50 in the same cell area covered by one of the access nodes or in the cell areas of a cluster of access nodes, are switched and controlled locally, by means of a local network 80 covering the cell areas of the access node 20 or cluster of access nodes. Local users are manually provisioned in the local network 80.
In this second approach there is no integration with any operator network whatsoever, since this system provides a solution designed to provide a emergency or temporary network. In fact, only users provisioned in the system can make calls.